1. Field of the Invention
The present invention relates to a method for attaching a first carrier device to a second carrier device in producing a micromechanical components.
2. Description of Related Art
In manufacturing a micromechanical component, two or more carrier devices, e.g., wafers and/or substrates, are attached to one another. The carrier devices, which are made of a semiconductor material, plastic, glass and/or a metal and may also be referred to as workpiece carriers, are often attached to one another in such a way that they remain permanently joined in subsequent operation of the micromechanical component.
For fixedly joining the at least two carrier devices, a plurality of wafer-bonding methods is known. In a first category of wafer-bonding methods without using a bond layer as an intermediate layer, chemical and/or physical effects are used for attaching the at least two carrier devices to one another. For example, hydrophilic and hydrophobic surfaces are brought into contact at a temperature above 1000° C. under a high pressure for silicon direct bonding, so that a tight bond is formed between the at least two carrier devices via hydrogen bridges and van der Waals interactions.
In a second category of wafer-bonding methods, at least one bond layer is situated as an intermediate layer between the at least two carrier devices. The at least one bond layer includes a material, a material composition and/or multiple material components, which are fusible by heating and produce a tight bond between the at least two carrier devices after cooling. It is also conceivable for a bond layer, which is brought into contact and heated to form a bond joint having a melting point below or above the melting point of the bond layers, to be situated on the at least two carrier devices. The phase diagram of this bond joint ideally has a eutectic point. For example, a method for eutectic bonding using a germanium layer and an aluminum layer is described in US Patent Application Publication 2006/0208326 A1.
Such wafer-bonding methods of the second category may additionally be used to produce an electrical contact between two carrier devices. For example, bond pads are provided as an intermediate layer on the first carrier device. The second carrier device is then attached to the bond pads, which function as electrical contacts.
However, problems often occur in fusing at least one bond layer situated between two carrier devices, preventing a tight bond from being formed between the two carrier devices and/or resulting in damage to a function-carrying structure on one of the two carrier devices due to the molten material of the at least one bond layer. In eutectic bonding, for example, an oxide layer between two adjacent bond layers may prevent mixing of the materials to form a bond-joining layer. It is therefore desirable to have an inexpensive option for ensuring advantageous mixing and/or spreading behavior of the material of the at least one bond layer in a bonding method.